DIN 913 / ISO 4026 Socket Set Screw with Flat Point A4 Stainless

DIN 913 / ISO 4026 — Socket Set Screw with Flat Point | A4 Marine Stainless Steel

FULLERKREG DIN 913 / ISO 4026 socket set screws (grub screws) with flat point are manufactured to full DIN and ISO dimensional standards in A4 marine-grade stainless steel (SUS 316) with a bright passivated surface finish. The A4 grade provides superior corrosion resistance compared to A2, making these set screws the preferred choice for marine, coastal, chemical, and high-humidity environments where chloride exposure is a concern.

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Product Specifications

Parameter	Detail
Standard	DIN 913 / ISO 4026
Type	Socket Set Screw (Grub Screw) — Flat Point
Drive	Hexagon Socket (Hex Allen Key)
Material	A4 Marine Stainless Steel (SUS 316 / 1.4401)
Surface Treatment	Bright Passivated (Electrochemical Passivation)
Thread	Metric Coarse Thread (ISO 68-1)
Thread Tolerance	6H (internal) / 6g (external) per ISO 965
Property Class	A4-70 (per ISO 3506-3)
Size Range	M1.6 — M24
Length Range	2 mm — 60 mm (size-dependent)
Point Type	Flat Point
Head Type	Fully Threaded, Headless (Grub)
RoHS Compliant	Yes

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Key Dimensions (DIN 913 / ISO 4026)

Thread (d)	Hex Key Size (s)	Min. Thread Engagement	Flat Point Dia. (dp) approx.	Common Lengths
M1.6	0.7 mm	0.8 mm	0.80 mm	2, 3, 4, 5 mm
M2	0.9 mm	1.0 mm	1.00 mm	2, 3, 4, 5, 6 mm
M2.5	1.3 mm	1.25 mm	1.50 mm	3, 4, 5, 6, 8 mm
M3	1.5 mm	1.5 mm	2.00 mm	3, 4, 5, 6, 8, 10 mm
M4	2.0 mm	2.0 mm	2.50 mm	4, 5, 6, 8, 10, 12 mm
M5	2.5 mm	2.5 mm	3.50 mm	5, 6, 8, 10, 12, 16 mm
M6	3.0 mm	3.0 mm	4.00 mm	6, 8, 10, 12, 16, 20 mm
M8	4.0 mm	4.0 mm	5.50 mm	8, 10, 12, 16, 20, 25 mm
M10	5.0 mm	5.0 mm	7.00 mm	10, 12, 16, 20, 25, 30 mm
M12	6.0 mm	6.0 mm	8.50 mm	12, 16, 20, 25, 30, 40 mm
M16	8.0 mm	8.0 mm	12.00 mm	16, 20, 25, 30, 40, 50 mm
M20	10.0 mm	10.0 mm	15.00 mm	20, 25, 30, 40, 50, 60 mm
M24	12.0 mm	12.0 mm	18.00 mm	25, 30, 40, 50, 60 mm

All dimensions per DIN 913 / ISO 4026. Consult FULLERKREG datasheet or contact us for full tolerance tables.

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Material & Surface Finish

A4 Marine Stainless Steel (SUS 316)

• Composition: 16–18% Chromium, 10–14% Nickel, 2–3% Molybdenum, ≤0.08% Carbon (austenitic stainless steel)
• Key Advantage: The addition of 2–3% Molybdenum significantly enhances resistance to pitting and crevice corrosion in chloride-containing environments — the critical differentiator over A2 (304)
• Corrosion Resistance: Excellent resistance to seawater, salt spray, brine, dilute acids, and most industrial chemicals
• Magnetic: Non-magnetic in annealed state; may become slightly magnetic after cold working
• Temperature Range: Suitable for −196°C to +400°C continuous service
• Tensile Strength: Min. 700 MPa (A4-70 per ISO 3506-3)
• Proof Load Stress: Min. 450 MPa
• Hardness: Max. 220 HV (Vickers)

A4 vs. A2 — Why Choose Marine Grade?

Property	A2 (SUS 304)	A4 (SUS 316)
Chromium Content	18%	16–18%
Nickel Content	8–10%	10–14%
Molybdenum	None	2–3% (key differentiator)
Chloride Resistance	Moderate	Superior
Marine / Saltwater Use	Not recommended	Recommended
Chemical Resistance	Good	Excellent
Pitting Resistance (PRE)	~18	~24–26
Property Class	A2-70	A4-70
Tensile Strength	Min. 700 MPa	Min. 700 MPa

Bright Passivated Surface Finish

• Electrochemical passivation removes free iron and surface contaminants from the stainless steel surface
• Restores and enhances the natural chromium oxide passive layer for maximum corrosion resistance
• Produces a bright, clean, silver appearance — no coating thickness added, no dimensional change
• Compliant with ASTM A967 / ISO 16048 passivation standards
• No risk of hydrogen embrittlement (no electroplating involved)
• Particularly important for A4 grade: passivation maximizes the effectiveness of the molybdenum-enhanced passive film

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Flat Point — Design & Function

The flat point is the most versatile set screw tip geometry. It provides a broad, flat contact surface against the mating shaft or component, making it ideal for:

• Non-marring clamping — does not indent or damage polished or soft shafts
• Frequent adjustment — can be loosened and repositioned without leaving permanent marks
• Hardened shafts — distributes clamping force over a larger area, reducing point stress
• Thin-walled components — lower risk of deformation compared to cup or cone points
• Locking against rotation — friction-based holding when tightened against a flat on the shaft

Flat Point vs. Other Set Screw Point Types

Point Type	Standard	Best For	Shaft Marking
Flat Point	DIN 913 / ISO 4026	Non-marring, frequent adjustment, hardened shafts	None / Minimal
Cup Point	DIN 916 / ISO 4029	Permanent locking, soft shafts, high torque	Circular indent
Cone Point	DIN 914 / ISO 4027	Permanent location, V-groove shafts	Deep indent
Dog Point	DIN 915 / ISO 4028	Precise location, keyway-free shafts	None (pin engagement)
Oval Point	ISO 4026 variant	Curved surfaces, pivot points	Minimal

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Typical Applications

The combination of A4 marine stainless steel and flat point geometry makes these set screws particularly suited for demanding environments:

• Marine & Offshore: Boat fittings, deck hardware, rigging components, underwater equipment, and offshore platforms exposed to seawater and salt spray
• Coastal & Outdoor Installations: Architectural hardware, outdoor signage, and structural components in high-humidity or salt-air environments
• Chemical Processing: Equipment handling dilute acids, chlorides, and corrosive process fluids where A2 would be insufficient
• Food & Beverage: Processing machinery, conveyors, and filling equipment requiring hygienic, corrosion-resistant fasteners (A4 preferred over A2 for wash-down environments)
• Pharmaceutical & Medical: Clean-room equipment and sterilizable assemblies requiring non-reactive, non-magnetic fasteners
• Swimming Pools & Water Treatment: Pump housings, filtration systems, and pool hardware exposed to chlorinated water
• Electronics & Instrumentation: Non-magnetic assemblies in sensitive measurement or imaging equipment
• General Machinery: Securing pulleys, gears, cams, and collars to shafts where corrosion resistance is required

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Installation Guidelines

• Thread engagement: Minimum engagement length = 1× nominal diameter (e.g., M6 requires min. 6 mm engagement)
• Tightening torque: Use a calibrated torque wrench; refer to ISO 898-1 / ISO 3506 torque tables for A4-70
• Lubrication: Apply anti-galling compound (e.g., molybdenum disulfide paste or PTFE-based lubricant) to prevent thread galling — especially important for stainless-to-stainless assemblies
• Hex key: Use the correct size hex key (Allen key) — see dimension table above; worn keys risk cam-out and socket damage
• Shaft flat: For maximum holding power, machine a flat on the shaft at the set screw contact point
• Locking: For vibration-prone applications, use thread-locking adhesive (medium strength) or nylon patch set screws
• Do not over-torque: Stainless steel has lower hardness than alloy steel; over-torquing risks thread stripping or socket rounding
• Dissimilar metals: When fastening into aluminum or other dissimilar metals in marine environments, consider using an anti-corrosion barrier compound to prevent galvanic corrosion

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Recommended Tightening Torques (A4-70, Dry)

Thread	Torque (N·m) — Reference
M2	0.08 N·m
M2.5	0.17 N·m
M3	0.30 N·m
M4	0.70 N·m
M5	1.40 N·m
M6	2.40 N·m
M8	5.80 N·m
M10	11.5 N·m
M12	20.0 N·m
M16	49.0 N·m
M20	96.0 N·m

Reference values for dry, unlubricated A4-70 stainless. Reduce by 15–20% when using lubricant or anti-galling compound. Always verify with your engineering team for safety-critical applications.

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Standards & Compliance

• DIN 913 — Socket set screws with hexagon socket and flat point
• ISO 4026 — Hexagon socket set screws with flat point
• ISO 3506-3 — Mechanical properties of corrosion-resistant stainless steel fasteners (set screws); A4-70 property class
• DIN 267-11 — Technical delivery conditions for fasteners; stainless steel property classes
• ISO 965-1 — Metric screw thread tolerances
• ASTM A967 / ISO 16048 — Passivation of stainless steel
• RoHS 2011/65/EU — Restriction of hazardous substances compliant

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Packaging & Ordering

• Available in standard retail packs, engineering bulk packs, and full-box quantities
• Custom quantity packaging available for OEM and wholesale customers
• Each pack labeled with: Part number, Thread size × Length, Material (A4), Standard (DIN 913 / ISO 4026), Quantity
• Bulk orders: contact FULLERKREG for volume pricing and lead times

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Quality Assurance

• 100% dimensional inspection on critical sizes per DIN 913 / ISO 4026
• Material certification (Mill Test Certificate) available on request — confirms A4 / SUS 316 composition including Molybdenum content
• Hardness and tensile testing per ISO 3506-3 batch requirements
• Thread gauge inspection (Go/No-Go) per ISO 965
• Salt spray corrosion testing available for qualification batches
• Traceability: heat number and batch records maintained

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Frequently Asked Questions

Q: What is the difference between DIN 913 and ISO 4026?
A: DIN 913 and ISO 4026 are technically equivalent standards for socket set screws with flat point. DIN 913 is the German standard; ISO 4026 is the international equivalent. Dimensions and tolerances are identical — parts are fully interchangeable.

Q: Why choose A4 over A2 stainless steel?
A: A4 (SUS 316) contains 2–3% Molybdenum, which is not present in A2 (SUS 304). This addition dramatically improves resistance to pitting and crevice corrosion in chloride environments such as seawater, salt spray, swimming pools, and chemical processing. For any application involving chloride exposure, A4 is the correct choice.

Q: Can A4 stainless set screws be used in seawater immersion?
A: A4 (316) stainless steel performs well in seawater splash and spray environments and is suitable for intermittent seawater immersion. For continuous full immersion in seawater, higher-grade alloys (e.g., duplex stainless or super-austenitic grades) may be required depending on temperature and chloride concentration. Contact FULLERKREG for guidance on extreme marine applications.

Q: Will the flat point damage my shaft?
A: The flat point is specifically designed to minimize shaft damage. It distributes clamping force over a broad area rather than concentrating it at a point. For polished or precision shafts, the flat point is the recommended choice.

Q: What hex key (Allen key) size do I need?
A: Refer to the dimension table above. Examples: M3 requires a 1.5 mm hex key; M6 requires a 3.0 mm hex key; M10 requires a 5.0 mm hex key.

Q: How do I prevent galling when installing stainless set screws?
A: Apply a small amount of anti-galling lubricant (molybdenum disulfide paste or PTFE-based compound) to the threads before installation. Avoid over-torquing and use a calibrated torque wrench. Galling is a particular risk with stainless-to-stainless assemblies and should always be mitigated with lubrication.

Q: Are these RoHS compliant?
A: Yes. FULLERKREG A4 stainless set screws are manufactured without restricted hazardous substances and are RoHS 2011/65/EU compliant.

Q: How can I verify the material is genuine A4 / SUS 316?
A: FULLERKREG provides Mill Test Certificates (MTC) on request, confirming the chemical composition including Molybdenum content. This is the standard method for verifying A4 / 316 grade in engineering and procurement.

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FULLERKREG — Precision Fasteners to DIN / ISO Standards. For technical support, custom sizes, or bulk quotations, please contact our engineering team.